176 SPECIAL ANATOMY OF THE SKELETON 



Infraspinatus below; to the interval between the two lips, the Levator anguli 

 scapulae is inserted; above the triangular surface at the commencement of the spine, 

 the Rhomboideus minor to the edge of that surface; the Rhomboideus major 

 is attached by means of a fibrous arch connected above to the lower part of 

 the triangular surface at the base of the spine, and below to the lower part of the 

 posterior border. 



Angles. The internal angle (angulus medialis), formed by the junction of the 

 superior and internal borders, is thin, smooth, rounded, somewhat inclined 

 outward, and gives attachment to a few fibres of the Levator anguli scapulae 

 muscle. 



The inferior angle (angulus inferior), thick and rough, is formed by the union 

 of the vertebral and axillary borders, its posterior surface affording origin to the 

 Teres major and frequently to a few fibres of the Latissimus dorsi. 



The external angle (angulus lateralis) is the thickest part of the bone, and forms 

 what is called the head of the scapula. The head presents a shallow, pyriform, 

 articular surface, the glenoid surface or cavity (cavitas glenoidalis), the longest 

 diameter of which is from above downward, and its direction outward and for- 

 ward. It is broader below than above. Just above it is a rough surface, the 

 supraglenoid tubercle (tuberositas supraglenoidalis), from which arises the long 

 tendon of the Biceps muscle. The glenoid cavity is covered with cartilage in 

 the recent state; and its margins are slightly raised and give attachment to a 

 fibrocartilaginous structure, the glenoid ligament, by which its cavity is deepened. 

 The neck of the scapula (collum scapulae) is the slightly depressed surface which 

 surrounds the head; it is more distinct on the posterior than on the anterior surface, 

 and below than above. In the latter situation it has arising from it a thick promi- 

 nence, the coracoid process. 



The coracoid process (processus coracoideus) is a thick, curved process of bone 

 which arises by a broad base from the upper part of the neck of the scapula; it 

 is directed at first upward and inward, then, becoming smaller, it changes its 

 direction and passes forward and outward. The ascending portion, flattened from 

 before backward, presents in front a smooth, concave surface over which passes 

 the Subscapularis muscle. The horizontal portion is flattened from above 

 downward, its upper surface is convex and irregular; its under surface is smooth; 

 its inner border is rough, and gives attachment to the Pectoralis minor; its outer 

 border is also rough for the coracoacromial ligament, while the apex is embraced 

 by the conjoined tendon of origin of the short head of the Biceps and of the 

 Coracobrachialis and gives attachment to the costocoracoid ligament. At the 

 inner side of the root of the coracoid process is a rough impression for the attach- 

 ment of the conoid ligament; and running from it obliquely forward and outward 

 on the upper surface of the horizontal portion, an elevated ridge for the attachment 

 of the trapezoid ligament. 



Structure. In the head, processes, and all the thickened parts of the bone the scapula is 

 composed of cancellous tissue covered by compact bone, while in the rest of its extent it is com- 

 posed of a thin layer of dense, compact tissue. The central part of the supraspinous fossa and 

 the upper part of the infraspinous fossa, but especially the former, are usually so thin as to 

 be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent 

 muscles come into contact. 



Development (Fig. 140). From seven or more centres one for the body, two for the 

 coracoid process, two for the acromion, one for the vertebral border, and one for the inferior 

 angle. Ossification of the body of the scapula commences about the second month of fetal life 

 by the formation of an irregular quadrilateral plate of bone immediately behind the glenoid 

 cavity. This plate extends itself so as to form the chief part of the bone, the spine growing 

 up from its posterior surface about the third month. . At birth a large part of the scapula is 

 osseous, but the glenoid cavity, coracoid and acromion processes, the posterior border, and 

 inferior angle are cartilaginous. From the fifteenth to the eighteenth month after birth 



